1. Technical Field
The present disclosure relates generally to wireless communication devices and, more specifically, to a method of monitoring and managing reference signals to extend standby time.
2. Background Information
Mobile subscribers consider long battery life to be a positive attribute of a mobile device, such as a cell phone. Battery life is typically described in terms of talk time and standby time. Even when a mobile subscriber is not carrying on a conversation, the cell phone still consumes power. Standby time is the length of time a battery can power a cell phone even when no calls are made. When a cell phone is turned on, the cell phone typically first acquires reference signals (also called pilot signals) before transmitting and receiving voice traffic over a traffic channel. For example, in some radio technologies, pilot signals are received over pilot, synchronization and paging channels. Once pilot signals are acquired, power is conserved by shutting down certain circuitry in the cell phone until a call is received or made. Other circuitry, however, must nevertheless be powered to detect whether the cell phone is receiving a call. Certain circuitry is turned on periodically to monitor the pilot signals transmitted over the pilot, synchronization and paging channels.
Even periodically monitoring pilot signals, however, consumes power. More power is consumed when the mobile device is operated in a heterogeneous network environment in which pilot signals are received from multiple wireless communication systems implementing multiple radio technologies. For example, a cell phone may be operated in a heterogeneous network environment in which access points operate using differing modulation techniques, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA) and the modulation protocol defined by 3GPP LTE. CDMA modulation is employed by the radio technologies of cdma2000 and Universal Terrestrial Radio Access (UTRA). TDMA modulation is used by the Global System for Mobile Communications (GSM). OFDMA is used by radio technologies such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20 and Flash-OFDM. Monitoring the multiple pilot signals received from access points that implement these various radio technologies consumes a significant amount of power.
Less power is consumed if pilot signals are acquired less frequently and if complex computations are performed less frequently on the pilot signals that are acquired. Standby time increases when fewer pilot signals are acquired and when fewer computations are performed on those acquired pilot signals. Thus, a method is sought for extending standby time by prioritizing and efficiently managing pilot signals received from heterogeneous access points.